JP7874730B2 - Cooling apparatus for metal strips, heat treatment equipment for metal strips, and method for cooling metal strips - Google Patents

Description

This disclosure relates to a cooling device for metal strips, a heat treatment facility for metal strips, and a method for cooling metal strips.

In the manufacturing process of metal strips, the metal strip may be rapidly cooled after heating in order to obtain a metal strip with desired properties.

Patent Document 1 discloses a continuous metal strip processing line equipped with a rapid cooling section that includes a nozzle for spraying a liquid or a mixture of a gas and a liquid. In this continuous metal strip processing line, the rapid cooling section cools the strip at a rate between 400°C/second and 1200°C/second by spraying the aforementioned liquid or mixture onto the strip from the nozzle.

Special Publication No. 2020-513480

In the manufacturing process of metal strips, it is desirable to efficiently cool the metal strip during rapid cooling, etc.

In view of the above circumstances, at least one embodiment of the present invention aims to provide a cooling device for a metal strip, a heat treatment facility for a metal strip, and a method for cooling a metal strip that are capable of efficiently cooling the metal strip.

A cooling device for a metal strip according to at least one embodiment of the present invention,
A cooling device for cooling a moving metal strip,
The metal strip is provided with a plurality of nozzles, each configured to spray a cooling medium onto the surface of the metal strip.
Among the effective collision areas of the plurality of nozzles, the ratio La/Ln of the length La of the non-effective collision area in the direction of travel of the metal strip between adjacent pairs of effective collision areas in the direction of travel and the distance Ln between the centers of the pair of effective collision areas in the direction of travel is 0.2 or more and 0.6 or less.
The effective impact area is the region in which the impact density of the liquid contained in the cooling medium sprayed from the nozzle onto the surface of the metal strip is 50% or more of the maximum value on the surface.

Furthermore, the heat treatment equipment for metal strips according to at least one embodiment of the present invention is
A furnace for heat-treating metal strips,
The above-described cooling device is configured to cool the metal strip that has been heat-treated in the furnace,
It is equipped with.

Furthermore, the method for cooling a metal strip according to at least one embodiment of the present invention is:
A cooling method for cooling a moving metal strip using a cooling device that includes multiple nozzles,
The process includes a step of cooling the metal strip by spraying a cooling medium onto the surface of the metal strip from the plurality of nozzles,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the ratio La/Ln of the length La of the non-effective collision area in the direction of travel of the metal strip between a pair of adjacent effective collision areas in the direction of travel of the metal strip, and the distance Ln between the centers of the pair of effective collision areas in the direction of travel of the metal strip, is 0.2 or more and 0.6 or less.
The effective impact area is the region in which the impact density of the liquid contained in the cooling medium sprayed from the nozzle onto the surface of the metal strip is 50% or more of the maximum value on the surface.

According to at least one embodiment of the present invention, a cooling device for a metal strip, a heat treatment device for a metal strip, and a method for cooling a metal strip are provided that enable efficient cooling of the metal strip.

This is a schematic diagram of a heat treatment facility for metal strips to which a cooling device according to one embodiment is applied. This is a schematic diagram of a cooling device according to one embodiment, viewed from the thickness direction of the metal strip. This is a schematic diagram illustrating the effective spray area of the nozzle. This is a diagram illustrating the configuration of a cooling device according to one embodiment. This is a diagram illustrating the configuration of a cooling device according to one embodiment. This graph shows the relationship between the ratio La/Ln and the heat transfer coefficient between the cooling medium sprayed onto the metal strip. This graph shows the relationship between the length of the effective collision zone Le and the heat transfer coefficient between the cooling medium sprayed onto the metal strip. This figure shows the surface of a metal strip being cooled by a cooling device according to one embodiment, viewed from the thickness direction. This figure shows the surface of a metal strip being cooled by a cooling device according to one embodiment, viewed from the thickness direction. This figure shows the surface of a metal strip being cooled by a cooling device according to one embodiment, viewed from the thickness direction. This diagram schematically shows multiple effective collision regions Re arranged in the width direction of the metal strip. This diagram schematically shows multiple effective collision regions Re arranged in the width direction of the metal strip. This graph shows an example of the time-dependent temperature change of a specific part of a metal strip during heat treatment.

Hereinafter, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

(Configuration of the heat treatment equipment)
Figure 1 is a schematic diagram of a heat treatment facility for metal strips to which a cooling device according to one embodiment is applied. As shown in the figure, the heat treatment facility 100 includes a first furnace (not shown) for heating the metal strip S (for example, steel strip), rolls 6 for conveying the metal strip S, and a cooling device 1 for cooling the metal strip S heated in the first furnace. That is, the cooling device 1 may be provided downstream of the first furnace in the conveying direction of the metal strip S. The arrows in Figure 1 indicate the conveying direction (traveling direction, moving direction) of the metal strip S.

In the exemplary embodiment shown in Figure 1, the metal strip S is transported vertically (from bottom to top in the illustrated example) between rolls 6, 6 that are spaced apart vertically. A pair of guide rolls 8, 8 are provided between the rolls 6, 6 so as to sandwich the metal strip S, thereby suppressing bending and twisting of the metal strip S.

The cooling device 1 is configured to cool a moving metal strip. The cooling device 1 includes a pair of ejection units 10, 10 provided on both sides of the pass line of the metal strip S in the thickness direction (plate thickness direction) of the metal strip S. The pair of ejection units 10, 10 are configured to eject a cooling medium toward the surface of the metal strip S. In this way, the metal strip S can be effectively cooled by blowing the cooling medium from the ejection units 10, 10 toward the surface of the metal strip S.

Although not specifically shown in the figures, in some embodiments, the cooling device 1 may be configured to cool a metal strip S that is being transported (traveling) along a top-down or horizontal direction. In this case, the cooling device 1 may include a jet unit provided on at least one of the two sides of the metal strip S in the thickness direction (i.e., the vertical direction).

The heat treatment equipment 100 may include a second furnace (not shown; i.e., a furnace located downstream of the cooling device 1 in the direction of transport of the metal strip S) for reheating the metal strip S cooled by the cooling device 1.

Figure 2 is a schematic diagram of a cooling device 1 according to one embodiment, viewed from the thickness direction of the metal strip S. As shown in Figure 2, the ejection unit 10 includes a plurality of nozzles 16, each configured to spray a cooling medium toward the surface of the metal strip S. The plurality of nozzles 16 constitute a plurality of nozzle rows 14 arranged along the travel direction (conveying direction) of the metal strip S. Each of the plurality of nozzle rows 14 is composed of a plurality of nozzles 16 arranged along the width direction of the metal strip S. The cooling medium may be water, a liquid mainly composed of water, or a mixture of the two with a gas.

Each of the multiple nozzle rows 14 may be provided on a header section 12 configured to supply a cooling medium. The header section 12 and the multiple nozzles 16 provided on the header section 12 are in communication, and the cooling medium supplied to the header section is sprayed toward the surface of the metal strip S by the multiple nozzles 16. As shown in Figures 1 and 2, the multiple header sections 12, each extending along the width direction of the metal strip S, may be arranged along the direction of travel of the metal strip S. The header section 12 may have a box-shaped form that extends along the width direction of the metal strip S.

Here, the effective impact area of the nozzle 16 will be explained with reference to Figure 3. Figure 3 is a schematic diagram illustrating the effective injection area of the nozzle 16. Figure 3 schematically shows the impact area R0 and the effective impact area Re, which are areas on the surface of the metal strip S where the cooling medium 17 sprayed from the nozzle 16 and the liquid contained in the cooling medium 17 collide. Note that Figure 3 shows the impact area R0 and the effective impact area Re when the surface of the metal strip S is viewed from above.

Graph (a) in Figure 3 shows the relationship between the position on the x-axis (straight line Lx) extending in a first direction (direction indicated by arrow a) on the surface of the metal strip S and the collision density W (amount of liquid supplied per unit time, per unit area) of the liquid contained in the cooling medium sprayed from a nozzle 16 on that surface. Graph (b) in Figure 3 shows the relationship between the position on the y-axis (straight line Ly) extending in a second direction (direction indicated by arrow b) perpendicular to the first direction on the surface of the metal strip S and the collision density W of the liquid contained in the cooling medium sprayed from the nozzle 16 on that surface. The x-axis and y-axis intersect at the center of the collision region R0 (center of the effective collision region Re).

In this specification, the effective impact area Re (see Figure 3) of the nozzle 16 is the region within the impact area R0 (see Figure 3) where the liquid contained in the cooling medium 17 sprayed from the nozzle 16 onto the surface of the metal strip S collides with the surface of the metal strip S, where the impact density W of the liquid contained in the cooling medium 17 sprayed from the nozzle 16 onto the surface of the metal strip S is 50% or more of its maximum value.

In the example shown in Figure 3, on the x-axis (straight line Lx), the collision density W is at its maximum value Wmax at the center position x0 of the collision region R0, and at both ends x1 and x2 the collision density W is 50% of the maximum value (Wmax/2). On the y-axis (straight line Ly), the collision density W is at its maximum value Wmax at the center position y0 of the collision region R0, and at both ends y1 and y2 the collision density W is 50% of the maximum value (Wmax/2). The effective collision region Re is the region enclosed by the contour Re*, which includes the region between x1 and x2 on the x-axis and the region between y1 and y2 on the y-axis.

In the example shown in Figure 3, the contour Re* of the effective collision area Re has a shape formed by connecting a pair of semicircular arcs (SC1, SC2) with two parallel straight lines (SL1, SL2). Furthermore, the length of the effective collision area Re in the first direction is a, and its length in the second direction is b.

Figures 4 and 5 are diagrams illustrating the configuration of a cooling device 1 according to one embodiment. Figure 4 is a schematic diagram showing an example of a plurality of effective impact regions Re formed on the surface of a metal strip S by a plurality of nozzles 16 constituting the cooling device 1. Figure 5 is a schematic diagram showing a pair of adjacent effective impact regions Re in the direction of travel of the metal strip S, and a pair of cooling media 17 forming the pair of effective impact regions Re.

As shown in Figure 4, multiple effective impact areas Re are formed on the surface of the metal strip S by multiple nozzles 16. The arrangement of the multiple effective impact areas Re has a shape corresponding to the arrangement of the multiple nozzles 16 (shown by dashed lines). The multiple effective impact areas Re shown in Figure 4 have the same shape as each other. Each of the multiple effective impact areas Re shown in Figure 4 has a shape that extends along the straight line L1 in the figure. The straight line L1 is inclined with respect to the width direction of the metal strip S. The inclination angle of the straight line L1 with respect to the width direction is θ.

As shown in Figure 5, among the effective collision regions Re (see Figure 4) of the multiple nozzles 16, an ineffective collision region Rn is formed between a pair of adjacent effective collision regions Re in the direction of travel of the metal strip S.

In a typical embodiment, for example as shown in Figure 4, adjacent pairs of effective collision regions Re in the direction of travel of the metal strip S have the same shape, but adjacent pairs of effective collision regions Re may have different shapes.

In some embodiments, the ratio La/Ln of the length La of the non-effective collision area Rn between a pair of adjacent effective collision areas Re in the direction of travel of the metal strip S, to the distance Ln between the centers of the pair of effective collision areas Re in the direction of travel of the metal strip S, is 0.2 or more and 0.6 or less.

Furthermore, a pair of adjacent effective collision regions Re in the direction of travel of the metal strip S may be the effective collision regions Re of a pair of nozzles 16, 16 included in the same nozzle row 14 (for example, nozzles 16A and 16B in Figure 4) (for example, effective collision regions Re-A and Re-B in Figure 4). In Figure 4, the distance Ln between the centers of the pair of effective collision regions Re-A and Re-B in the direction of travel of the metal strip S is d1, and the length La of the non-effective collision region Rn between the pair of effective collision regions Re-A and Re-B in the direction of travel of the metal strip S is c1.

Alternatively, a pair of adjacent effective collision regions Re in the direction of travel of the metal strip S may be the effective collision regions Re of a pair of nozzles 16, 16 (for example, nozzles 16A, 16C in Figure 4) included in adjacent nozzle rows 14, 14 in the direction of travel of the metal strip S (for example, effective collision regions Re-A and Re-C in Figure 4). In Figure 4, the distance Ln between the centers of the pair of effective collision regions Re-A and Re-C in the direction of travel of the metal strip S is d2, and the length La of the non-effective collision region Rn between the pair of effective collision regions Re-A and Re-C in the direction of travel of the metal strip S is c2.

Figure 6 is a graph showing the relationship between the ratio La/Ln (horizontal axis) and the heat transfer coefficient (vertical axis) between the metal strip S and the cooling medium sprayed onto it. The heat transfer coefficient in the graph is the measurement result when the metal strip S at 400°C is cooled by spraying water onto it. These heat transfer coefficient measurements were obtained while changing the ratio La/Ln and while changing the collision density of the liquid contained in the cooling medium on the surface of the metal strip S.

As can be seen from the graph in Figure 6, the heat transfer coefficient is high when the above-mentioned ratio La/Ln is between 0.2 and 0.6. In other words, when the above-mentioned ratio La/Ln is between 0.2 and 0.6, the cooling efficiency of the metal strip S by the cooling medium sprayed from the nozzle 16 of the cooling device 1 is high. The reason for this is thought to be as follows.

In other words, in the above-described embodiment, since the ratio La/Ln is 0.2 or more, a certain degree of width can be secured in the direction of travel of the metal strip S for the non-effective collision areas Rn formed between the effective collision areas Re. Therefore, the liquid contained in the cooling medium ejected from the nozzle 16 and impacting the surface of the metal strip S can leave the surface of the metal strip S via the non-effective collision areas Rn without remaining in the effective collision areas Re. This makes it less likely for the supply of newly ejected cooling medium to the surface of the metal strip S to be hindered, and the cooling efficiency is improved. Furthermore, in the above-described embodiment, since the ratio La/Ln is 0.6 or less, the non-effective collision areas Rn that do not contribute to the cooling of the metal strip S are not too wide in the direction of travel of the metal strip S. Therefore, the width of the effective collision areas Re in the direction of travel of the metal strip S can be maintained, and the cooling efficiency is improved. Thus, according to the above-described embodiment, the metal strip S can be cooled efficiently.

In some embodiments, the above-mentioned ratio La/Ln is 0.45 or more and 0.5 or less.

As can be seen from the graph in Figure 6, the heat transfer coefficient is particularly high when the above-mentioned ratio La/Ln is between 0.45 and 0.5. In other words, when the above-mentioned ratio La/Ln is between 0.45 and 0.5, the cooling efficiency of the metal strip S by the cooling medium sprayed from the nozzle 16 of the cooling device 1 is particularly high.

In other words, in the above-described embodiment, since the ratio La/Ln is 0.45 or more, a larger area of the non-effective impact area Rn formed between effective impact areas Re can be secured. As a result, the supply of the cooling medium newly ejected from the nozzle 16 to the surface of the metal strip S is less likely to be obstructed, and the cooling efficiency is further improved. Furthermore, in the above-described embodiment, since the ratio La/Ln is 0.5 or less, the non-effective impact area Rn that does not contribute to the cooling of the metal strip S can be made narrower. Therefore, the effective impact area Re can be widened, and the cooling efficiency is further improved. Thus, according to the above-described embodiment, the metal strip S can be cooled more efficiently.

In some embodiments, the length Le of each of the pair of effective collision areas Re described above in the direction of travel of the metal strip S is 80 mm or more and 140 mm or less.

Furthermore, in Figure 4, the length Le of each metal strip S in the direction of travel of the pair of effective collision regions Re-A and Re-B is b1. The length Le of each metal strip S in the direction of travel of the pair of effective collision regions Re-A and Re-C in Figure 4 is also b1.

Figure 7 is a graph showing the relationship between the length Le of the effective impact area Re in the direction of travel of the metal strip S (horizontal axis) and the heat transfer coefficient (vertical axis) between the metal strip S and the cooling medium sprayed onto the metal strip S. The heat transfer coefficient in the graph is the measurement result when the metal strip S at 400°C is cooled by spraying water onto the metal strip S. These heat transfer coefficient measurement results were obtained while changing the length Le mentioned above, and while changing the impact density of the liquid contained in the cooling medium on the surface of the metal strip S.

As can be seen from the graph in Figure 7, the heat transfer coefficient is high when the length Le is between 80 mm and 140 mm. In other words, the cooling efficiency of the metal strip S by the cooling medium sprayed from the nozzle 16 of the cooling device 1 is high when the length Le is between 80 mm and 140 mm. The reason for this is thought to be as follows.

In other words, in the above-described embodiment, since the length Le of the effective impact area Re of the nozzle 16 is 80 mm or more, it takes a certain amount of time for the metal strip S to pass through the effective impact area Re. As a result, while the metal strip S is passing through the effective impact area Re, the surface temperature of the metal strip S is more likely to move from the film boiling region to the transition boiling region. Therefore, the metal strip S can be cooled more efficiently. Also, in the above-described embodiment, since the length Le of the effective impact area Re of the nozzle 16 is 140 mm or less, the distance that the liquid film formed in the effective impact area Re travels to the non-effective impact area Rn is relatively short. Therefore, the liquid film formed in the effective impact area Re is more likely to flow out into the non-effective impact area Rn and can smoothly separate from the surface of the metal strip S via the non-effective impact area Rn. This makes it less likely that the supply of the cooling medium newly ejected from the nozzle 16 to the surface of the metal strip S will be hindered, and the cooling efficiency will be further improved. Therefore, according to the above-described embodiment, the metal strip can be cooled more efficiently.

Furthermore, if the temperature transitions from the film boiling region to the transition boiling region during cooling in one effective collision zone Re, the heat flux from the surface of the metal strip S to the liquid increases rapidly, and the temperature is easily maintained at the transition boiling region until the next effective collision zone Re is entered, thus the temperature of the metal strip S decreases smoothly. In contrast, if cooling only progresses to just before the transition boiling region during cooling in one effective collision zone Re, the surface temperature of the metal strip S recovers (rises), and when the next effective collision zone Re is entered, cooling starts again from the film boiling region, reducing the cooling efficiency. In this respect, as mentioned above, it is advantageous for the length of the effective collision zone Re to be somewhat longer.

Figures 8 to 10 are views of the surface of a metal strip S being cooled by a cooling device 1 according to one embodiment, viewed from the thickness direction, and schematically show the effective impact area Re of the nozzle 16 of the cooling device 1. In the example shown in Figures 8 to 10, there is an effective impact area Re for each of the multiple nozzles 16, and the arrangement of the multiple effective impact areas Re has a shape corresponding to the arrangement of the multiple nozzles 16.

In some embodiments, as shown in Figure 8, for example, the effective impact area Re of the nozzle 16 is circular. That is, the contour Re* of the effective impact area Re has an arc shape.

In some embodiments, each of the multiple effective impact areas Re shown in Figures 9 and 10 has a shape that extends in a direction along the width direction of the metal strip S (in the direction of the straight line L1).

In some embodiments, as shown in Figures 9 and 10, for example, the effective impact area Re of the nozzle 16 has a shape having a first axis La extending along the width direction of the metal strip S (or in the direction of the straight line L1), and a second axis Lb extending in a direction intersecting the first axis La, where the length of the first axis La is longer than the length of the second axis Lb. Note that the first axis La being along the width direction of the metal strip S means that the angle θ of the first axis La with respect to the width direction (shown by the straight line LW) is less than 45 degrees. In the exemplary embodiments shown in Figures 9 and 10, the first axis La and the second axis Lb are orthogonal to each other.

In the above embodiment, the effective impact area Re has a shape having a first axis La along the width direction of the metal strip S and a second axis Lb intersecting the first axis La. Since the first axis La is longer than the second axis Lb, the length of the effective impact area Re in the direction of travel of the metal strip S (the direction intersecting the width direction) is less likely to become excessively long. Therefore, the liquid contained in the cooling medium sprayed from the nozzle 16 can easily move from the effective impact area Re to the non-effective impact area Rn (see Figure 3), and can easily separate smoothly from the surface of the metal strip S via the non-effective impact area Rn without remaining in the effective impact area Re. As a result, the supply of newly ejected cooling medium from the nozzle 16 to the surface of the metal strip S is less likely to be hindered, and the cooling efficiency is further improved.

In some embodiments, the first axis La described above is inclined with respect to the width direction of the metal strip S. That is, in some embodiments, the angle θ of the first axis La with respect to the width direction of the metal strip S (direction of the straight line LW) (see Figure 9 or Figure 10) is greater than 0.

In this case, focusing on a specific widthwise position, the proportion of the region where the effective collision area Re exists in the direction of travel of the metal strip S can be increased compared to the case where the first axis La is not tilted with respect to the widthwise direction of the metal strip S (i.e., when the first axis La is parallel to the widthwise direction). Therefore, uneven cooling in the direction of travel of the metal strip S can be suppressed, which makes it easier to manufacture a metal strip S of good quality.

In some embodiments, the angle θ is 18 degrees or less.

In the above-described embodiment, since the angle θ is 18 degrees or less, the timing of the cooling of the metal strip S entering the effective collision region Re does not differ significantly depending on its position in the width direction. Therefore, the difference in the timing at which the surface temperature of the metal strip S reaches its transition boiling point in the width direction can be reduced. Thus, uneven cooling in the width direction of the metal strip S can be suppressed more effectively.

In some embodiments, the angle θ is between 5 degrees and 15 degrees.

In the above-described embodiment, since the angle θ is between 5 and 15 degrees, uneven cooling in the running direction and width direction of the metal strip S can be suppressed even more effectively. Therefore, it becomes easier to manufacture metal strips of good quality.

In some embodiments, as shown in Figure 9, for example, the effective impact area Re of the nozzle 16 has an elliptical shape with a first axis La along the width direction of the metal strip S as the major axis and a second axis Lb perpendicular to the first axis La as the minor axis.

In some embodiments, as shown in Figure 10, for example, the contour of the effective impact area Re of the nozzle 16 has a shape formed by connecting a pair of semicircular arcs SC1 and SC2 with two straight lines SL1 and SL2. In the exemplary embodiment shown in Figure 10, the pair of semicircular arcs SC1 and SC2 have the same radius, and the two straight lines SL1 and SL2 are parallel to each other. Hereinafter, for convenience, the shape formed by a pair of semicircular arcs and two parallel straight lines connecting the semicircular arcs, as shown in Figure 10, will be referred to as an elliptical shape.

In the above-described embodiment, the contour Re* of the effective impact area Re has a shape formed by connecting a pair of semicircular arcs SC1 and SC2 with two straight lines SL1 and SL2. This allows for a wider region where the cumulative amount of cooling medium sprayed over the entire length of the metal strip S in the direction of travel is uniform in the width direction. Therefore, uneven cooling in the width direction of the metal strip S can be reduced more effectively.

Figures 11 and 12 schematically show a plurality of effective collision regions Re (Re1 to Re5) arranged in the width direction of the metal strip S. Each of these effective collision regions Re has an oval shape (see Figure 10). In the example shown in Figures 11 and 12, each of the plurality of effective collision regions Re1 to Re5 extends along the width direction of the metal strip S, and its length (length of the major axis) is a. The angle between the extension direction of the plurality of effective collision regions Re1 to Re5 (direction of the major axis; direction shown by the straight line L1) and the width direction of the metal strip S is θ (where 0 degrees < θ < 45 degrees). The major axes of the plurality of effective collision regions Re1 to Re5 have endpoints A1 to A5 on one side and endpoints B1 to B5 on the other side in the width direction of the metal strip S, respectively.

In some embodiments, among a plurality of effective collision regions arranged in the width direction of the metal strip S, the distance L in the width direction of the metal strip S between the endpoint A of one effective collision region Re (for example, Re1 in Figures 11 and 12) and the endpoint B (B4 in Figures 11 and 12) of another effective collision region Re (effective collision region Re4 in Figures 11 and 12) that has the endpoint B closest to the endpoint A of the first effective collision region Re (A1 in Figures 11 and 12) in the width direction of the metal strip S, the length a of the major axis of the effective collision region Re, and the angle θ of the major axis with respect to the width direction are related by the following formula (a).
-0.1≦L/(a×cos(θ))≦0.1...(a)

In the width direction of the metal strip S, the number of effective collision areas that the metal strip S passes through when traveling a distance equal to the length of the effective collision area Re (a × sin(θ)) differs between the section Ra between the endpoint A of one effective collision area Re (for example, endpoint A1 of effective collision area Re1) and the endpoint B of another effective collision area Re (for example, endpoint B4 of effective collision area Re4) and the other section Rb.

For example, in Figure 11, when the metal strip S travels a distance equal to the length of the effective collision area Re (a × sin(θ)), it passes through two effective collision areas Re in section Ra, while it passes through three effective collision areas Re in section Rb. Similarly, in Figure 12, when the metal strip S travels a distance equal to the length of the effective collision area Re (a × sin(θ)), it passes through four effective collision areas Re in section Ra, while it passes through three effective collision areas Re in section Rb.

Therefore, if the length (L) of section Ra other than section Rb, which occupies the majority of the plate width direction, is shorter than the length (a × cos(θ)) of the effective collision area Re in the plate width direction, it becomes easier to suppress temperature unevenness in the plate width direction after passing through the effective collision area Re. Thus, by satisfying the above equation (a) with respect to the distance L, the length a of the major axis of the effective collision area Re, and the angle θ of the major axis with respect to the width direction, it is possible to more effectively suppress cooling unevenness in the metal strip S after cooling.

Figure 13 is a graph showing an example of the time change in temperature of a specific part of a metal strip S when the metal strip S is heat-treated using a cooling method according to several embodiments.

As shown in Figure 13, in some embodiments, at time t0, a metal strip S at temperature T0 is heated in a first furnace to raise its temperature to T1, and then maintained at temperature T1 until time t1. Between time t1 and t2, the metal strip S is cooled to a temperature of approximately T2 using the cooling device 1 described above (cooling step). After that, the metal strip S is heated in a second furnace, and the temperature of the metal strip S is maintained at T2 between time t3 and t4.

The temperature T1 mentioned above may be 600°C or higher. The temperature T2 mentioned above may be in the range of 100°C to 400°C. That is, in the cooling step described above, a cooling medium may be sprayed onto the surface of the metal strip S at 600°C or higher from the nozzle 16 of the cooling device 1 to cool the metal strip S to a temperature range of 100°C to 400°C. Furthermore, after the cooling step, the temperature of the metal strip S may be maintained within the temperature range of 100°C to 400°C.

The heat treatment described above, that is, a heat treatment in which the metal strip S is heated to a high temperature of 600°C or higher, then rapidly cooled to a temperature range of 100°C to 400°C, and then maintained at that temperature range, may be applied to the manufacturing process of electrical steel sheets and high-tensile steel.

In some embodiments, the cooling step described above may involve spraying a cooling medium onto the surface of the metal strip S from multiple nozzles 16 so that the cooling rate of the metal strip S is 500°C per second or more. Alternatively, the cooling step described above may involve spraying the cooling medium onto the metal strip S so that the amount of cooling medium sprayed per square meter of the surface of the metal strip S is 500 liters per minute or more. By using the cooling device 1 described above in the cooling step, the metal strip S can be rapidly cooled efficiently.

The contents described in each of the above embodiments can be understood, for example, as follows:

(1) A cooling device for a metal strip (1) according to at least one embodiment of the present invention is
A cooling device for cooling a moving metal strip (S),
The metal strip is provided with a plurality of nozzles (16) each configured to spray a cooling medium onto the surface of the metal strip.
Among the effective collision areas (Re) of the plurality of nozzles, the ratio La/Ln of the length La of the non-effective collision area (Rn) in the direction of travel of the metal strip between a pair of adjacent effective collision areas in the direction of travel and the distance Ln between the centers of the pair of effective collision areas in the direction of travel is 0.2 or more and 0.6 or less.
The effective impact area is the region in which the impact density of the liquid contained in the cooling medium sprayed from the nozzle onto the surface of the metal strip is 50% or more of the maximum value on the surface.

According to the configuration described in (1) above, the cooling device includes multiple nozzles, and effective collision zones for each of the multiple nozzles are formed on the surface of the metal strip. Furthermore, since the ratio La/Ln of the length La of the non-effective collision zone between a pair of adjacent effective collision zones in the direction of travel of the metal strip and the distance Ln between the centers of the pair of effective collision zones is 0.2 or more and 0.6 or less, the metal strip can be cooled efficiently. The reason for this is thought to be as follows.
In other words, in the above configuration, since the ratio La/Ln is 0.2 or more, a certain amount of width can be secured in the direction of travel of the metal strip for the ineffective collision zones formed between the effective collision zones. Therefore, the liquid contained in the cooling medium ejected from the nozzle and impacting the surface of the metal strip can leave the surface of the metal strip via the ineffective collision zones without remaining in the effective collision zones. As a result, the supply of newly ejected cooling medium to the surface of the metal strip is less likely to be hindered, and the cooling efficiency is improved. Furthermore, in the above configuration, since the ratio La/Ln is 0.6 or less, the ineffective collision zones that do not contribute to cooling are not too wide in the direction of travel of the metal strip. Therefore, the width of the effective collision zones in the direction of travel of the metal strip can be maintained, and the cooling efficiency is improved. Thus, according to the above configuration (1), the metal strip can be cooled efficiently.

(2) In some embodiments, in the configuration of (1) above,
The ratio La/Ln of the length La of the non-effective collision area in the direction of travel to the center-to-center distance Ln is 0.45 or more and 0.5 or less.

According to the configuration of (2) above, since the above-mentioned ratio is 0.45 or more and 0.5 or less, the metal strip can be cooled more efficiently. That is, in the above configuration, since the above-mentioned ratio La/Ln is 0.45 or more, a larger area of the non-effective impact area formed between the pair of effective impact areas in the direction of travel of the metal strip can be secured, so as described above, the supply of the cooling medium newly ejected from the nozzle to the surface of the metal strip is less likely to be obstructed, and the cooling efficiency is further improved. Also, in the above configuration, since the above-mentioned ratio La/Ln is 0.5 or less, the non-effective impact area that does not contribute to cooling can be made narrower in the direction of travel of the metal strip. Therefore, the effective impact area can be widened in the direction of travel of the metal strip, and the cooling efficiency is further improved. Thus, according to the configuration of (2) above, the metal strip can be cooled more efficiently.

(3) In some embodiments, in the configuration of (1) or (2) above,
The length Le of each of the pair of effective collision areas in the aforementioned direction of travel is 80 mm or more and 140 mm or less.

In the configuration of (3) above, since the length Le of the effective impact area of the nozzle in the direction of travel of the metal strip is 80 mm or more, it takes a certain amount of time for the metal strip to pass through the effective impact area. As a result, the surface temperature of the metal strip is more likely to move from the film boiling region to the transition boiling region while the metal strip is passing through the effective impact area. Therefore, the metal strip can be cooled more efficiently. Also, in the configuration of (3) above, since the length Le of the effective impact area of the nozzle is 140 mm or less, the distance that the liquid film formed in the effective impact area travels to the non-effective impact area in the direction of travel of the metal strip is relatively short. Therefore, the liquid film formed in the effective impact area flows out into the non-effective impact area and can smoothly separate from the surface of the metal strip via the non-effective impact area. This makes it less likely for the supply of the cooling medium newly ejected from the nozzle to the surface of the metal strip to be hindered, and the cooling efficiency is further improved. Therefore, according to the configuration of (3) above, the metal strip can be cooled more efficiently.

(4) In some embodiments, in any of the configurations (1) to (3) above,
The effective collision area has a shape having a first axis (La) along the width direction of the metal strip and a second axis (Lb) intersecting the first axis.
The first axis is longer than the second axis.

According to the configuration of (4) above, the effective impact area has a shape having a first axis along the width direction of the metal strip and a second axis intersecting the first axis, and since the first axis is longer than the second axis, the length of the effective impact area in the direction of travel of the metal strip (the direction intersecting the width direction) is less likely to become excessively long. Therefore, the liquid contained in the cooling medium sprayed from the nozzle can easily move from the effective impact area to the non-effective impact area, and can easily separate smoothly from the surface of the metal strip via the non-effective impact area without remaining in the effective impact area. As a result, the supply of newly ejected cooling medium to the surface of the metal strip is less likely to be hindered, and the cooling efficiency is further improved. Therefore, according to the configuration of (4) above, the metal strip can be cooled more efficiently.

(5) In some embodiments, in the configuration of (4) above,
The first axis is inclined with respect to the width direction.

According to the configuration of (5) above, since the first axis is inclined with respect to the width direction of the metal strip, the proportion of the region where the effective collision area exists in the direction of travel of the metal strip can be increased compared to the case where the first axis is not inclined with respect to the width direction of the metal strip. Therefore, uneven cooling in the direction of travel of the metal strip can be suppressed, which makes it easier to manufacture metal strips of good quality.

(6) In some embodiments, in the configuration of (5) above,
The angle (θ) of the first axis with respect to the width direction is 18 degrees or less.

According to the configuration described in (6) above, since the angle of the first axis with respect to the width direction of the metal strip is 18 degrees or less, the timing of the cooling of the metal strip entering the effective collision area does not differ significantly depending on the position in the width direction. Therefore, the difference in the timing at which the surface temperature of the metal strip reaches the transition boiling temperature in the width direction of the sheet can be reduced. Thus, uneven cooling in the width direction of the metal strip can be suppressed, which makes it easier to manufacture metal strips of good quality.

(7) In some embodiments, in the configuration of (6) above,
The angle of the first axis with respect to the width direction is between 5 degrees and 15 degrees.

According to the configuration described in (7) above, since the angle of the first axis with respect to the width direction of the metal strip is 5 degrees or more and 15 degrees or less, uneven cooling in the running direction and width direction of the metal strip can be more effectively suppressed. Therefore, it becomes easier to manufacture metal strips of good quality.

(8) In some embodiments, in any of the configurations (4) to (7) above,
The contour of the effective collision area (Re*) has a shape formed by connecting a pair of semicircular arcs with two straight lines.

According to the configuration described in (8) above, the contour of the effective impact area has a shape formed by connecting a pair of semicircular arcs with two straight lines, so that the region in which the cumulative value of the amount of refrigerant sprayed over the entire length of the metal strip in the direction of travel is uniform in the width direction can be widened. Therefore, uneven cooling in the width direction of the metal strip can be reduced more effectively.

(9) A heat treatment apparatus (100) for metal strips according to at least one embodiment of the present invention,
A furnace for heat-treating metal strips,
A cooling device (1) according to any one of the above items (1) to (8), configured to cool the metal strip that has been heat-treated in the furnace,
It is equipped with.

According to the configuration described in (9) above, the cooling device includes multiple nozzles, and effective collision zones of each of the multiple nozzles are formed on the surface of the metal strip. Furthermore, since the ratio La/Ln of the length La of the non-effective collision zone between a pair of adjacent effective collision zones in the direction of travel of the metal strip and the distance Ln between the centers of the pair of effective collision zones is 0.2 or more and 0.6 or less, the metal strip can be cooled efficiently. The reason for this is thought to be as follows.
In other words, in the above configuration, since the ratio La/Ln is 0.2 or more, a certain amount of width can be secured in the direction of travel of the metal strip for the ineffective collision zones formed between the effective collision zones. Therefore, the liquid contained in the cooling medium ejected from the nozzle and impacting the surface of the metal strip can leave the surface of the metal strip via the ineffective collision zones without remaining in the effective collision zones. As a result, the supply of newly ejected cooling medium to the surface of the metal strip is less likely to be hindered, and the cooling efficiency is improved. Furthermore, in the above configuration, since the ratio La/Ln is 0.6 or less, the ineffective collision zones that do not contribute to cooling are not too wide in the direction of travel of the metal strip. Therefore, the width of the effective collision zones in the direction of travel of the metal strip can be maintained, and the cooling efficiency is improved. Thus, according to the above configuration (9), the metal strip can be cooled efficiently.

(10) A method for cooling a metal strip according to at least one embodiment of the present invention is:
A cooling method for cooling a moving metal strip (S) using a cooling device (1) that includes a plurality of nozzles (16),
The process includes a step of cooling the metal strip by spraying a cooling medium onto the surface of the metal strip from the plurality of nozzles,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the ratio La/Ln of the length La of the non-effective impact area (Rn) in the direction of travel of the metal strip, between a pair of adjacent effective impact areas (Re) of the plurality of nozzles, and the distance Ln between the centers of the pair of effective impact areas in the direction of travel, is 0.2 or more and 0.6 or less.
The effective impact area is the region in which the impact density of the liquid contained in the cooling medium sprayed from the nozzle onto the surface of the metal strip is 50% or more of the maximum value on the surface.

According to the method described in (10) above, the cooling device includes multiple nozzles, and effective collision zones of each of the multiple nozzles are formed on the surface of the metal strip. Furthermore, since the ratio La/Ln of the length La of the non-effective collision zone between a pair of adjacent effective collision zones in the direction of travel of the metal strip and the distance Ln between the centers of the pair of effective collision zones is 0.2 or more and 0.6 or less, the metal strip can be cooled efficiently. The reason for this is thought to be as follows.
In other words, in the above configuration, since the ratio La/Ln is 0.2 or more, a certain amount of width can be secured in the direction of travel of the metal strip for the non-effective collision zones formed between the effective collision zones. Therefore, the liquid contained in the cooling medium ejected from the nozzle and impacting the surface of the metal strip can leave the surface of the metal strip via the non-effective collision zones without remaining in the effective collision zones. As a result, the supply of newly ejected cooling medium to the surface of the metal strip is less likely to be hindered, and the cooling efficiency is improved. Furthermore, in the above configuration, since the ratio La/Ln is 0.6 or less, the non-effective collision zones that do not contribute to cooling are not too wide in the direction of travel of the metal strip. Therefore, the width of the effective collision zones in the direction of travel of the metal strip can be maintained, and the cooling efficiency is improved. Thus, the metal strip can be efficiently cooled by the method of (10) above.

(11) In some embodiments, in the method of (10) above,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip from the plurality of nozzles such that the amount of cooling medium sprayed onto one square meter of the surface of the metal strip is 500 liters per minute or more.

According to the method described in (11) above, the amount of cooling medium sprayed onto the metal strip is 500 liters or more per square meter of surface area. Therefore, when rapidly cooling a metal strip in this manner, the metal strip can be cooled efficiently.

(12) In some embodiments, in the method of (10) or (11) above,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip at a temperature of 600°C or higher to cool the metal strip to a temperature range of 100°C to 400°C.

According to the method described in (12) above, a cooling medium is sprayed onto a metal strip at a temperature of 600°C or higher to cool the metal strip to a temperature range of 100°C to 400°C. Therefore, when cooling a metal strip in this temperature range, the metal strip can be cooled efficiently.

(13) In some embodiments, in any of the methods described in (10) to (12) above,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the length Le of the effective collision area in the direction of travel is 80 mm or more and less than 140 mm.

In the method described in (13) above, since the length Le of the effective impact area of the nozzle in the direction of travel of the metal strip is 80 mm or more, it takes a certain amount of time for the metal strip to pass through the effective impact area. As a result, the surface temperature of the metal strip is more likely to move from the film boiling region to the transition boiling region while the metal strip is passing through the effective impact area. Therefore, the metal strip can be cooled more efficiently. Also, in the method described in (13) above, since the length Le of the effective impact area of the nozzle is 140 mm or less, the distance that the liquid film formed in the effective impact area travels to the non-effective impact area in the direction of travel of the metal strip is relatively short. Therefore, the liquid film formed in the effective impact area flows out into the non-effective impact area and can smoothly separate from the surface of the metal strip via the non-effective impact area. This makes it less likely for the supply of the cooling medium newly ejected from the nozzle to the surface of the metal strip to be obstructed, and the cooling efficiency is further improved. Therefore, the metal strip can be cooled more efficiently according to the method described in (13) above.

(14) In some embodiments, in any of the methods described in (10) to (13) above,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the effective impact area has a first axis (La) along the width direction of the metal strip and a second axis (Lb) perpendicular to the first axis, and the first axis is longer than the second axis.

According to the method described in (14) above, the effective impact area has a shape having a first axis along the width direction of the metal strip and a second axis intersecting the first axis, and since the first axis is longer than the second axis, the length of the effective impact area in the direction of travel of the metal strip (the direction intersecting the width direction) is less likely to become excessively long. Therefore, the liquid contained in the cooling medium sprayed from the nozzle can easily move from the effective impact area to the non-effective impact area, and can easily separate smoothly from the surface of the metal strip via the non-effective impact area without remaining in the effective impact area. As a result, the supply of newly ejected cooling medium to the surface of the metal strip is less likely to be hindered, and the cooling efficiency is further improved. Therefore, according to the method described in (14) above, the metal strip can be cooled more efficiently.

(15) In some embodiments, in the method of (14) above,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip with the first axis tilted with respect to the width direction.

According to the method described in (15) above, since the first axis is inclined with respect to the width direction of the metal strip, the proportion of the region where an effective collision area exists in the direction of travel of the metal strip can be increased compared to the case where the first axis is not inclined with respect to the width direction of the metal strip. Therefore, uneven cooling in the direction of travel of the metal strip can be suppressed, which makes it easier to manufacture metal strips of good quality.

(16) In some embodiments, in the method of (14) or (15) above,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the contour of the effective impact area has a shape formed by connecting a pair of semicircular arcs with two straight lines.

According to the method described in (16) above, the contour of the effective impact area has a shape formed by connecting a pair of semicircular arcs with two straight lines, so that the region in which the cumulative value of the amount of refrigerant sprayed over the entire length of the metal strip in the direction of travel is uniform in the width direction can be widened. Therefore, uneven cooling in the width direction of the metal strip can be reduced more effectively.

Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

In this specification, expressions describing relative or absolute arrangements such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved.
For example, expressions such as "identical,""equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function.
Furthermore, in this specification, expressions describing shapes such as quadrilaterals and cylindrical shapes shall not only represent geometrically precise quadrilaterals and cylindrical shapes, but also shapes that include uneven surfaces, chamfered surfaces, etc., to the extent that the same effect can be achieved.
Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components.

1 Cooling device 6 Roll 8 Guide roll 10 Discharge unit 12 Header section 14 Nozzle rows 16, 16A-16C Nozzle 17 Cooling medium 100 Heat treatment equipment A (A1-A5) Endpoint B (B1-B5) Endpoint La First axis Lb Second axis Ln Distance between centers R0 Impact area Re Effective impact area Re* Contour Rn Ineffective impact area S Metal strip

Claims (15)

A cooling device for cooling a moving metal strip,
The metal strip is provided with a plurality of nozzles, each configured to spray a cooling medium onto the surface of the metal strip.
Among the effective collision areas of the plurality of nozzles, the ratio La/Ln of the length La of the non-effective collision area in the direction of travel of the metal strip between adjacent pairs of effective collision areas in the direction of travel and the distance Ln between the centers of the pair of effective collision areas in the direction of travel is 0.2 or more and 0.6 or less.
A cooling device for a metal strip, wherein the effective impact area is a region in which the impact density of the liquid contained in the cooling medium sprayed from the nozzle onto the surface of the metal strip is 50% or more of its maximum value on the surface. The cooling device for a metal strip according to claim 1, wherein the ratio La/Ln of the length La of the non-effective collision area in the direction of travel to the center-to-center distance Ln is 0.45 or more and 0.5 or less. The cooling device for a metal strip according to claim 1 or 2, wherein the length Le of each of the pair of effective collision areas in the direction of travel is 80 mm or more and 140 mm or less. The effective collision area has a shape having a first axis along the width direction of the metal strip and a second axis intersecting the first axis.
The cooling device for a metal strip according to claim 1 or 2, wherein the first axis is longer than the second axis. The cooling device for a metal strip according to claim 4, wherein the first axis is inclined with respect to the width direction. The cooling device for a metal strip according to claim 5, wherein the angle of the first axis with respect to the width direction is 18 degrees or less. The cooling device for a metal strip according to claim 6, wherein the angle of the first axis with respect to the width direction is 5 degrees or more and 15 degrees or less. The cooling device for a metal strip according to claim 4, wherein the contour of the effective collision area has a shape in which a pair of semicircular arcs are connected by two straight lines. A furnace for heat-treating metal strips,
A cooling device according to claim 1 or 2, configured to cool the metal strip that has been heat-treated in the furnace,
A heat treatment facility for metal strips equipped with the following features. A cooling method for cooling a moving metal strip using a cooling device that includes multiple nozzles,
The process includes a step of cooling the metal strip by spraying a cooling medium onto the surface of the metal strip from the plurality of nozzles,
In the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the ratio La/Ln of the length La of the non-effective collision area in the direction of travel of the metal strip between a pair of adjacent effective collision areas in the direction of travel of the metal strip, and the distance Ln between the centers of the pair of effective collision areas in the direction of travel of the metal strip, is 0.2 or more and 0.6 or less.
A method for cooling a metal strip, wherein the effective impact area is a region in which the impact density of the liquid contained in the cooling medium sprayed from the nozzle onto the surface of the metal strip is 50% or more of its maximum value on the surface. The method for cooling a metal strip according to claim 10, wherein in the cooling step, the cooling medium is sprayed onto the surface of the metal strip from the plurality of nozzles such that the amount of the cooling medium sprayed onto the surface of the metal strip per square meter is 500 liters per minute or more. The method for cooling a metal strip according to claim 10 or 11, wherein in the cooling step, the cooling medium is sprayed onto the surface of the metal strip at a temperature of 600°C or higher to cool the metal strip to a temperature range of 100°C to 400°C. The method for cooling a metal strip according to claim 10 or 11, wherein in the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the length Le of the effective collision area in the direction of travel is 80 mm or more and 140 mm or less. The method for cooling a metal strip according to claim 10 or 11, wherein in the cooling step, the cooling medium is sprayed onto the surface of the metal strip such that the effective impact area has a first axis along the width direction of the metal strip and a second axis intersecting the first axis, and the first axis is longer than the second axis. The method for cooling a metal strip according to claim 14, wherein in the cooling step, the first axis is tilted with respect to the width direction and the cooling medium is sprayed onto the surface of the metal strip.